Praxis Precision Medicines Inc. shares moved higher Monday after the U.S. Food and Drug Administration awarded Breakthrough Therapy Designation to elsunersen for the treatment of seizures associated with SCN2A Developmental and Epileptic Encephalopathy, a rare early-onset genetic epilepsy.
The FDA action referenced results from the EMBRAVE Part A trial, a randomized, sham-controlled Phase 1/2 study of elsunersen, which is an antisense oligonucleotide. In that trial, investigators reported a 77% sham-adjusted decrease in monthly seizure frequency. Praxis also noted that the improvement observed in EMBRAVE Part A was sustained through an open-label extension for as long as one year.
EMBRAVE Part A enrolled nine pediatric patients aged 2-12 years with early-seizure-onset SCN2A-DEE and tested ascending doses of elsunersen. In the randomized portion of the study, 71% of patients receiving elsunersen achieved a greater than 50% reduction in seizures, and 57% of those treated experienced at least a 28-day seizure-free interval during the six-month treatment period.
Following discussions with the FDA, Praxis converted its pivotal EMBRAVE3 trial to a single-arm, baseline-controlled registrational study, the company said. Under that design all enrolled patients receive elsunersen for 24 weeks and may continue in an additional 24-week treatment extension. EMBRAVE3 is expected to enroll roughly 30 patients and is proceeding under the streamlined pathway agreed with the agency.
In addition to Breakthrough Therapy designation, elsunersen holds multiple regulatory incentives from the FDA, including Orphan Drug and Rare Pediatric Disease designations. The therapy also has Orphan Drug and PRIME designations from the European Medicines Agency, according to Praxis.
Early-seizure-onset SCN2A-DEE is described by the company as a rare and severe genetic epilepsy that stems from gain-of-function variants in the SCN2A gene. Praxis notes there are no approved therapies that address the underlying genetic cause of this condition.
The FDA's Breakthrough Therapy designation signals that the agency recognizes preliminary clinical evidence that the drug may demonstrate substantial improvement over existing therapies for a serious condition. Praxis reported the EMBRAVE Part A findings as the basis for the designation, and the company is continuing its registrational trial under the single-arm approach aligned with the regulator.
Market reaction
Shares of Praxis rose following the announcement, reflecting investor response to the regulatory recognition and the robustness of the reported EMBRAVE Part A results. The company is advancing its pivotal study while holding multiple regulatory designations that may affect development and review timelines.